A pressure independent orifice equation for the estimation of diastolic mitral valve area in mitral insufficiency: correlation with cardiac catheterisation data using a radioactive Krypton indicator method for the determination of regurgitant filling volume

We have investigated the application of an hydraulic orifice equation for the computation of diastolic mitral valve area in conditions of regurgitation. The new equation is given by Af = 21 Vf/T2, where Af is the total forward flow mitral valve area in cm2, Vf is the diastolic filling volume in ml, T is the diastolic filling period and 21 is a discharge coefficient derived from clinical haemodynamic data. Areas computed by the new formula correlate with valve areas as computed by the Gorlin formula at a level given by r = 0.93, n = 27. The results suggest that the new formula may be utilised in the context of mitral insufficiency and further, considerating the nature of the haemodynamic variables involved, an echographic quantification of this condition by M-mode or bidimensional echocardiography may be possible.